Computational study of small-scale laminar coflow diffusion flames: influences of fuel dilution on the negative buoyant flame

Abstract

The effects of adding H2O and CO2 on the hydrodynamic structure of laminar diffusion hydrocarbon flame was investigated at atmospheric pressure, focusing on the recirculation zone in the vicinity of nozzle exit with buoyancy force applied to the fuel. H2O and CO2 diluent were used to dilute the propane fuel focusing on how these diluents affect the vortices inside the recirculation zones. To clarify the influence of diluents, H2O and CO2content (in mole basis %) in the fuel mixture was gradually increased from 0 to 20%. The numerical computations were performed using one-step gas-phase chemistry, thermal, and transport properties. The computational results of non-diluent propane fuel found to be in good agreement with available experimental data. The results showed that the fuel dilution notably influences the flow-field. In particular, the dilution of fuel with H2O and CO2 weakens the vortices formation. With increasing the diluents ratio, the scale of vortices structure becomes smaller. The results also showed that H2O -diluent was more effective in reducing the vortex scale compared with CO2-diluent.